[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([OH:12])=[C:6]([C:10]=1[OH:11])[C:7]([OH:9])=[O:8].[CH3:13][C:14]([CH3:16])=O.S(Cl)(Cl)=O>COCCOC.CN(C1C=CN=CC=1)C.O.C([O-])([O-])=O.[K+].[K+]>[Cl:1][C:2]1[CH:3]=[CH:4][C:5]2[O:12][C:14]([CH3:16])([CH3:13])[O:8][C:7](=[O:9])[C:6]=2[C:10]=1[OH:11]To a solution of 5-chloro-2,6-dihydroxybenzoic acid (Doyle, F. P. J. Chem. Soc., 1963, p. 497-506) (500 mg, 2.65 mmol) in DME (2 mL) was added DMAP (16.2 mg, 0.13 mmol) and acetone (200.2 mg, 3.45 mmol). The solution was cooled to 10° C. and thionyl chloride (448 mg, 3.77 mmol) was added over 10 min. The solution was allowed to overnight. The solution was diluted with water and neutralized with solid K2CO3 and the aqueous phase was extracted w/EtOAc. The combined organic layers were washed with water, brine and dried (Na2SO4). The crude residue was purified by column chromatography on silica gel to afford the product as yellow solid (162 mg, 27% yield). 1H NMR: 1.74 (s, 6H), 6.44 (d, 1H, J=8.0 Hz), 7.48 (d, 1H, J=8.0 Hz), 10.83 (s, 1H).
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